'83 RX-7 from <30 to 50+
 

So my S-10 progress is in the newb introductions part of this site, but yesterday I brought home a cherry '83 RX-7.
Those rotaries are supposed to average mid 20s at best, occasionally spiking to 30. But rotaries carbon-lock, and the cost of gaskets and apex seals exceeds the cost of a used piston engine.
So because my dad had a '96 Bonneville that did 35 MPG with the lockup torque converter not locking, I'm going with one of those engines. It's a 205-HP 3.8L V6, also found in '96-'02 Camaro / Firebird with manual transmissions.
I've talked to a PCM expert, this deal is good.
Classic V8s fit, so this swap will fit.
I see a smaller, lighter car with less drag than the "new" engine ever came in, and stock gearing for those cars gave as low as 1800 RPM at 65 MPH in the 'maro / 'bird, also known as the F-twins.
The five speed has a 0.72:1 OD, the 185/70R13 tires are 23.2" dia., and available axle ratios include 2.286:1, 2.412:1, 2.5625:1, 2.7333:1, 2.929:1, 3.077:1, and up into the mid-4s, because the RX-7 is getting a 7.5" rear axle from my '87 S-10, which is getting a Ford 8.8" rear axle.
I found a decent urethane airdam for $ 136 new, but that will have to wait until the car moves under its own power again. Today I unload it from the trailer, return the trailer, and begin pulling the rotary for disassembly.

Just ordered a set of 2.286:1 gears for $ 70 shipped.

You could make one heck of a sleeper by supercharging that 3.8

Pretty, pretty car. It's going to be nice having one back on the road.

Subscribed! If you gear it up, it should return decent top gear cruising economy (at reasonable speeds).

Have you done the math -- what will the cruising RPM be at X mph with that tall gearing?

1540 RPM @ 65 MPH, with the 195/55R15 tires I just ordered, because 185/70R13s are getting extremely scarce, and for this odd lug pattern, the best solution for me, after hours of trying to scheme a cheaper alternative, was a new set of Konig 15x7s made for this car, at $ 102.50 ea. The tires are $ 50 ea. Those prices include shipping.

Thanks!
As for manual at 98% efficient versus automatic at 86%, the Mustang crowd proved that false on chassis dynos, and the LSx Camaro crowd re-proved it. Manuals are around 86% efficient, while autos are around 78%.

Rear turbo, in place of the muffler, was thought about. But the factory supercharged ones used very little boost on an engine with different heads because the blower forced relocation of the injectors, plus the pistons and pins were different, the rods probably, the block and crank maybe.
So I'm getting a common L36 instead of the rare L67, which is overpriced, and in high demand by the Fiero guys.

I raced a 79 RX7 in showroom Stock SCCA many yrs ago.
Had a 4bbl 5 speed.
It LOVED being downshifted!!!!!!!

RX 7 road load
 

While the Mazda is lighter and smaller,the Pontiac had a lower Cd.The CdAs of the two cars might be closer than you think.
The weight difference won't mean anything on the open road.
If you're going for HWY mpg you're gonna have to do something to the back of the RX-7.It's contour is too aggressive and prone to attached longitudinal vortices.
http://i1271.photobucket.com/albums/...d2/06-2825.jpg

I rebuilt an RX2 many years ago. I am not so keen on automatics, though. I thought rx7s had a low CD, or maybe that's the next generation body.

cosmick- The sig isn't about that, it's about the infinite mpg you can get with a manual while the engine is off. ;)

Agreed, good dialog like yours is appreciated, and cD isn't difficult to improve, as my S-10 has proved to me. Much the same way the 5"-tall rear spoiler actually helps the '70-'81 Camaro / Firebird, even though it adds downforce, and the 2" rear spoiler on the '82-'92 Camaro is nothing but drag reduction, functionally (style is a matter of opinion) there are similar examples of spoilers reducing drag on late model cars ranging from Tauruses to Porsches.
So here I'm attaching an image that shows the rear spoiler I'm hunting for.

http://i1316.photobucket.com/albums/...ps893bd5f9.jpg

Even so, The plan is baseline the car, then try the airdam, then remove the airdam and try the spoiler, then try both together.
I'm not finding much for side skirts, but undercar airflow looks like something I might help with a belly tray.
I don't believe the Pontiac is all that good, it is the worst MPG in its class, even with its so-called ecotec engine, which may be a moniker getting slapped on several different families of 4 cylinders, and that pic looks nothing like wind tunnel test results I've found for similar cars.

Oh. So like turning it off when coasting down a mountain?

Engine braking's better then, but yeah. If inertia and/or gravity will do the job without using gasoline...

RX-7 aero
 

*The Mazda suffers too much slope.The centerline flow may be attached due to downwash but its accompanied by high drag vortices
http://i1271.photobucket.com/albums/...ntitled313.jpg
*'relaxing' the roofline helps
http://i1271.photobucket.com/albums/...ntitled314.jpg
*When you hit the Koenig/Kamm aft-body contour you can be separation and vorticity free
http://i1271.photobucket.com/albums/...ohead2/209.jpg
*The hashed lines behind the RX-7 indicate the volume of space which is compromised by it's body design,leading to Cd 0.38 instead of Cd 0.10 as with
http://i1271.photobucket.com/albums/...ead2/Solar.jpg
http://i1271.photobucket.com/albums/...ohead2/602.jpg

There's something worth pondering, thanks!
Just pulled an L36 from a '96 Camaro, brought it home. Going after the trans tomorrow morning. Also scored a 28-spline 2-series Auburn, for under $ 50. Then got the new rotors, now that I've had them in my hands I think I can make them work.
The gears arrived, I expected 39:17, got 48:21, so that's 2.2857:1, but should always be loading 2 teeth at a time, on both the ring and on the pinion.

Got the transmission.

Great looking car! That spoiler is sweet is well. I'll be following.

Mooresville,N.C.
 

OG,have you been to the Aerodyne/A2 wind tunnel? It's in your backyard.:)

Parts I ordered are beginning to arrive. I'm not happy with the tires, but they'll do. I've decided on a 4WD S-10 rear axle housing, the 4-lug Mustang shafts, and redrill the '84 Trans Am rotors. Not the least possible unsprung weight, but the best parts for me.
Also gotta get a PCM and send it to Ryan Gick at gmtuners.com, he's been the best results at the best price on other projects.
Really not liking these exhaust manifolds, half hoping they won't fit the car.
Pics once most of the parts are here and the work gets underway.
Can't understand why it costs so much for shipping a simple airdam. It's not even 6' x 1' x 1', and not even 10 pounds with the box. I'm not paying $134 for shipping, I'll build my own instead.
My appreciation to those who've taken interest.

Snafu with the pilot bushing, otherwise waiting for parts to arrive.

Here're the 4 worst pics:

http://i1316.photobucket.com/albums/...psa80f6dcb.jpg

http://i1316.photobucket.com/albums/...psebbd66ac.jpg

http://i1316.photobucket.com/albums/...psff2000e4.jpg

http://i1316.photobucket.com/albums/...ps8232ee2e.jpg

Not too shabby.

I'm trying to show progress, triumphs and failures in how I do things, like my own big brakes, my own Watt's link, and fitting this engine, then the show stopping result. So now 3 good "before" pics, then 2 progress pics, including my first test-fit of the '94 Camaro gauge cluster.

http://i1316.photobucket.com/albums/...psf90533df.jpg

http://i1316.photobucket.com/albums/...pse86e9e4c.jpg

http://i1316.photobucket.com/albums/...ps182d47ce.jpg

The car is about to be painted blue, and there's been a snafu with some bolts.

http://i1316.photobucket.com/albums/...ps02b1a6ce.jpg

http://i1316.photobucket.com/albums/...ps806b117d.jpg

http://i1316.photobucket.com/albums/...ps8cc70be8.jpg

http://i1316.photobucket.com/albums/...psff2d1c72.jpg

http://i1316.photobucket.com/albums/...ps61383ab1.jpg

That's all for this morning.

Looking good. Are you painting it? What color blue? Is the engine getting any work done to it before going in?

The engine is staying stock for now, just a tune up and an oil change. It'll be a darker blue, not metallic nor pearlescent. The interior will end up mostly medium grey.

Today's progress, stripping and sanding towards Maaco.

http://i1316.photobucket.com/albums/...psafc5bf29.jpg

http://i1316.photobucket.com/albums/...psedb48374.jpg

http://i1316.photobucket.com/albums/...ps3336f4b8.jpg

Just got the later front suspension / steering / brakes / crossmember / anti-roll bar, except for the springs and struts. Ordered new KYB struts. Now back to the cosmetics.

Each different thread has different ideas about how thick of a spacer between the rear of the FC K-member and the SA framerails. I saw this as adjustable anti-dive, but then I'm having difficulty wading through all the search results for that. I'm thinking It safest to start with a stack of spacers totaling 1" thickness, then test drive very cautiously, then go 3/4" thickness, then test again, until I've tested down to no spacer.
Likewise, I think I'll be moving the FC K-member back about 1" to keep the front wheels from being too far forward in the wheelwells.
Comments welcome.

So a kind person in Washington, calling themself rk970, offered this:
The bottom of the FB frame rails are about 1.5" lower then the FC. When you put in the FC sub frame the front roll center will be "under ground" (on a FC at normal ride height the control arms go up hill toward the center about 5/8"). To low of a roll center equates to lots of weight transfer to the outside tire, dartness/twichy handling and bump steer problems. Now if you section the ends off of the FC subframe and plate it to fit between the frame rails in the proper location for ride height you can correct the roll center. You would also have to section the frame rail to clear the tie rods.
A roll center that is to low will give quick transitions turning left to right. Do not mistake quick transitions for good a "good" handling car.
So now I post this:
More work, but possibly more return on investment. Thank you very much for sharing that.
I guess I will check hood clearance for this V6 just bolting it to the existing pair of front bolts for the subframe, then get to sectioning as practical.
As to the rear suspension, I'm going for a 3-link, with the car's stock lower trailing arms, possibly shortened an inch or 2 so they don't attach behind the axle, that looks stupid, and a top center link, possibly the same length as the lowers, then move the Watt's link to be chassis-mounted, behind the bottom center of the axle. To attach it to the axle, I bought 2 feet of 1.5" x 1.5" x 0.1875" mild steel square tubing. I'll weld this to the leaf spring pads GM welded to the bottoms of the tubes, and have them extend far enough back to clear the diff. Speedway offers a kit for $ 70 that will help, Watts Link - Speedway Motors, America's Oldest Speed Shop
and I got a pivot off a '98 Lincoln.
Yesterday I redrilled one rotor successfully, and made progress on the "new" axle.

http://i1316.photobucket.com/albums/...psf450d9a9.jpg

http://i1316.photobucket.com/albums/...psb8d3c46e.jpg

http://i1316.photobucket.com/albums/...psb2a31d06.jpg

http://i1316.photobucket.com/albums/...ps3d97a357.jpg

http://i1316.photobucket.com/albums/...ps4068c7ad.jpg

http://i1316.photobucket.com/albums/...ps8f9de9b5.jpg

http://i1316.photobucket.com/albums/...ps1967ebae.jpg

Oooh, parts. I like parts. :)

It was easier to figure out an affordable and easy brake upgrade for the '83 front end than for my FC subframe swap. I know that some 12" brakes can fit in some 15" wheels, and since I'm now forced into using the 4-lug 15" wheels, 12" is what I'm working on. Sure, I was going to go 11" before, but now finding a wrecked FC with the optional 11" 4-piston 5-lug fronts isn't realistic.

Between sanding Bondo, spraying primer, and dying the interior parts, I've been studying Napaonline.
If I want to use Mazda calipers, the NB4886041 is 11.88" x 0.87", and $ 42 ea. But I think I want more. I think the next step, playing it safe, is NB4886777, which is just 11.7", but is 1.03" thick, for using the Camaro calipers I have. That's $ 46 per rotor. Either of those are likely to require having their center holes enlarged. And they're both 5 on 4.5, so I'd have to drill 3 new holes in each to make them 4-lug. That's not difficult.
If the 11.7s prove an easy fit, there are NB48880014, also 1.03", but 12.02" and $ 53 ea. Or if I want Mazda calipers and 4-lug without drilling, UP880192 is 12.01" x 0.87" for $ 49 ea.
But then we come to the other spec of cast rotors. The height. Napa gives these specs also, but if you have to make caliper brackets anyway, all that matters is if the height is too shallow for your calipers and your wheels.
If I like what I end up with, I'll offer copies of my brackets.
If I just wanted the biggest cheapest rotors, I found some 12.72" x 1.18" for $ 36 ea. Dunno what low-cost calipers they'd like.
Anyway, that's where my mind is while I'm nearing the deadline for Maaco.